2. 分区：小于pivot的放左边，大于的放右边
Resident doctors also have little control on where and when they are asked to work, and say that the need to do placements in different parts of the country can be expensive.
，更多细节参见91视频
// Sync variants return boolean (true = accepted)
第三十一条 任何个人和组织不得实施下列行为，非法推广相关应用程序、软件：